1. Field of the Invention
The present invention relates to a process for extracting a particular color image of an object and a color processing device for deriving geometrical characteristics including a location, area, and profile of the object from the process.
2. Description of the Prior Art
For identification or inspection of an object or component in a factory assembly line, there has been proposed to utilizes a television camera to obtain a black-and-white image of the object and to process the image for deriving geometric characteristics of the object. Such process based on the black-and-white image is only available for identification in terms of the geometric characteristics and is therefore not able to distinguish the object by its color. To this end, another prior art process has been proposed to use a color television camera providing a video signal indicating a color image of the object and to process the video signal in such a manner as to extract a color image with regard to a particular color for obtaining the geometrical characteristics based upon the particular or filtered color image of the object. The particular color is generally selected and determined by the users to be a combination of three primary colors each having a suitable range of level. That is, when considering a color space defined by a coordinate system having coordinates of the three primary colors, the particular color can be determined within the color space as corresponding to a limited zone having the limited ranges of levels with respect to the three primary colors, respectively. However, such determination of the color is found not to be practical and reliable since the levels of the three primary colors will vary as the objects is monitored in varying illumination levels. To overcome this problem, it is also contemplated to elongate the zone by a certain extent in order to compensate for the variation in the illumination level as described in Japanese Patent Publication [kokoku] No. 59-5944. Nevertheless, a critical problem remains in this process in that it can not select the hue, chroma, and brightness independently from each other. For example, it is not possible to extract an image of the object having the same chroma but having different hue.